#include<cstdio>
#include<deque>
using namespace std;
deque<int> q,r;
int n,m,v,i,j,k;
long long s;
int main ()
{
freopen("deque.in","r",stdin);
freopen("deque.out","w",stdout);
scanf("%d%d",&n,&k);
for(i=1;i<=n;i++)
    {
    scanf("%d",&j);
    while(!q.empty()&&j<q.back())
        {
        q.pop_back();
        r.pop_back();
        }
    q.push_back(j);
    r.push_back(i);
    if(i>=k)
        {
        s+=q.front();
        while(!r.empty()&&i-r.front()+1>=k)
            {
            r.pop_front();
            q.pop_front();
            }
        }
    }
printf("%lld",s);
}